Effect of clove oil on plant pathogenic bacteria and bacterial wilt of tomato and geranium

Authors: Huang, Qi; Lakshman, Dilip

Submitted to: Journal of Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/4/2011
Publication Date: 2/7/2011
Citation: Huang, Q., Lakshman, D.K. 2011. Effect of clove oil on plant pathogenic bacteria and bacterial wilt of tomato and geranium. Journal of Plant Pathology. 92(3):701-707.

Interpretive Summary: R. solanacearum causes bacterial wilt, a soil-borne vascular disease that is distributed worldwide and attacks over 450 plant species including ornamentals such as geranium. It also limits the production of such economically important crops as tomato, tobacco, potato and banana, and is very hard to control. In our study, we tested the effect of clove oil, a plant essential oil derived from the spice plant clove, on seven different genera of plant pathogenic bacteria and found that all bacteria tested were sensitive to clove oil, with R. solanacearum being the most sensitive one. We therefore explored the possibility of using this natural plant product as a pre-plant soil fumigant to control bacterial wilt of tomato and geranium caused by R. solanacearum. In our greenhouse experiments, we found that treatment of R. solanacearum-infested soil with 5 ml of clove oil formulation per kilogram of soil reduced population of R. solanacearum to undetectable level, and none of the tomato and geranium plants transplanted into such soil developed wilt symptoms or harbored the bacterium. Treatment of infested soil with 2 or 2.5 ml of clove oil per kilogram of soil also had a significant effect on bacterial wilt, since only a few tomato and geranium plants wilted and harbored the bacterium when grown in such soil. Our work will be of value primarily to plant pathologists and tomato and geranium growers interested in diseases caused by R. solanacearum and in utilizing natural plant products as an environmentally friendly alternative to the use of methyl bromide to combat plant soil-borne diseases.

Technical Abstract: We determined the antibacterial activity of clove oil against seven different genera of plant pathogenic bacteria including Gram-negative Agrobacterium tumefaciens, Erwinia carotovora pv. carotovora, Pseudomonas syringae pv. syringae, Ralstonia solanacearum, and Xanthomonas campestris pv. pelargonii, as well as Gram-positive Rhodococcus fascians and Streptomyces spp. Both Gram-positive and Gram-negative bacteria tested were sensitive to clove oil, with R. solanacearum being the most sensitive one. Greenhouse experiments were therefore conducted to determine the effect of clove oil as a pre-plant soil fumigant on bacterial wilt of tomato and geranium caused by R. solanacearum. Seven days after treating R. solanacearum-infested plant growth medium (“soil”) with 5 ml of clove oil per kilogram of soil (0.5%), populations of R. solanacearum were reduced to undetectable level, and none of the tomato and geranium plants transplanted into such soil developed wilt symptoms or harbored the bacterium. Treatment of infested soil with 2 or 2.5 ml of clove oil per kilogram of soil also had a significant effect on bacterial wilt, since only a few tomato and geranium plants wilted and harbored the bacterium when grown in such soil. Our results suggest that clove oil has the potential to be an alternative control measure to combat bacterial wilt of tomato and geranium.